Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.36	8.353%	$188.9243	$188.92	$188.90	$188.90
Purchase #2	$102.42	3.521%	$106.0262	$106.03	$106.05	$106.00
Purchase #3	$108.55	3.258%	$112.0866	$112.09	$112.10	$112.10
Purchase #4	$149.85	11.314%	$166.804	$166.80	$166.80	$166.80
Purchase #5	$47.40	12.561%	$53.3539	$53.35	$53.35	$53.40
Purchase #6	$170.50	12.379%	$191.6062	$191.61	$191.60	$191.60
Purchase #7	$141.29	6.470%	$150.4315	$150.43	$150.45	$150.40
7 purchase totals =	$894.37		$969.2327	$969.23	$969.25	$969.20